The present invention relates to a device for implantation in the heart of a mammal, with a generally tubular shape, and having a longitudinal axis, a first end and a second end, and a lumen permitting blood flow there through.
The present invention also relates to the use of such a device for treating tricuspid regurgitation in a mammal.
The human heart is subdivided by septa into right and left halves, and a constriction subdivides each half of the organ into two cavities, the upper cavity being called the atrium, the lower the ventricle, respectively. Thus, the heart consists of four chambers, i.e., right and left atria, and right and left ventricles. Via the four valves of the human heart, i.e. the aortic, mitral, tricuspid and pulmonary valves, a one-way blood flow through the (healthy) heart is maintained. Thus, the four heart valves make sure that blood always flows freely in a forward direction and that there is no backward leakage.
In the heart, blood flows from the right and left atria into the ventricles through the open tricuspid and mitral valves. When the ventricles are full, the tricuspid and mitral valves shut. This action, i.e. the closing of the tricuspid and the mitral valve, prevents blood from flowing backward into the atria while the ventricles contract. As the ventricles begin to contract, the pulmonic and aortic valves are forced open, thus pumping blood out of the ventricles: Blood present in the right ventricle passes through the open pulmonic valve into the pulmonary artery, and blood present in the left ventricle passes through the open aortic valve into the aorta where it is delivered to the rest of the body. When the ventricles finish contracting and begin to relax, the aortic and pulmonic valves shut. These valves prevent blood from flowing back into the ventricles.
With each heartbeat, this pattern is repeated, causing blood to flow continuously to the heart, lungs, and body. Due to their vital function, diseased or malfunctioning heart valves are a major threat for a person's life.
Several different kinds of valve disorders are known, such as stenosis, which occurs when a heart valve doesn't fully open due to stiff or fused leaflets preventing them from opening properly, or prolapse, where the valve flaps do not close smoothly or evenly but collapse backwards into the heart chamber they are supposed to be sealing off.
Valve regurgitation (backward flow) is also common problem, and occurs when a heart valve doesn't close tightly, as a consequence of which the valve does not seal and blood leaks backwards across the valve. This condition—also called valvular insufficiency—reduces the heart's pumping efficiency. When the heart contracts, blood is pumped forward in the proper direction but is also forced backwards through the damaged valve. As the leak worsens, the heart has to work harder to make up for the leaky valve and less blood may flow to the rest of the body. Depending on which valve is affected, the condition is called tricuspid regurgitation, pulmonary regurgitation, mitral regurgitation, or aortic regurgitation.
While mitral insufficiency has—likely due to its higher occurrence—been subject matter of many treatment approaches in recent years, tricuspid insufficiency, or rather its treatment has gained only little attention over the past years. Tricuspid insufficiency may be asymptomatic, however, common symptoms are, e.g. hepatomegaly, edema and jugular distenosis. As a result of the failure of the tricuspid valve to close properly, with each heart beat some blood passes from the right ventricle to the right atrium, the opposite of the normal direction. Although congenital causes of tricuspid insufficiency exist, most cases are due to annulus dilation and dilation of the right ventricle, and this dilation leads to a derangement of the normal anatomy and mechanics of the tricuspid valve and the muscles governing its proper function. The result is incompetence of the tricuspid valve.
However, isolated surgical tricuspid valve repair is seldom performed, and remains rather undertreated. Actually, most repairs are performed in the context with other planned cardiac surgeries.
The main therapy of tricuspid insufficiency is treatment of underlying cause, which is why in most cases surgery is not indicated since the root problem lies with a dilated or damaged right ventricle. Medical therapy with diuretics is the mainstay of treatment. Unfortunately, this can lead to volume depletion and decreased cardiac output. Indeed, one must often accept a certain degree of symptomatic tricuspid insufficiency in order to prevent a decrease in cardiac output. Treatment with medicines to reduce cardiac afterload may also be of benefit but a similar risk of depressed cardiac output applies.
Human heart valves may be replaced with mechanical valves, or with specially prepared heart valves from human or animal donors (known as bioprosthetic or tissue valves).
Bioprosthetic valves are sometimes called tissue valves and made from specially treated natural (“biological”) valves. These valves come from two sources: human donors and animals. Valves from animal sources (usually cows or pigs) are very similar to those found in the human heart.
Surgical repair or replacement of the tricuspid valve carries a high operative mortality. When applying surgical means, tricuspid regurgitation is rectified either by replacement of the total valve with a replacement valve or by constriction of the valve ring with an annular remodeling ring, which involves rigid or flexible annular bands, which are intended to reduce annular size.
Due to the high risk of surgical operations and due to the fact that in many cases a surgery is even impossible to perform, e.g. if the patient is inoperable or operable only at a too high surgical risk, transcatheter techniques and devices for tricuspid regurgitation treatment have recently been developed; however, only limited experimental transcatheter data is available.
E.g., WO 2012/018599 A1 discloses a two valve caval stent for functional replacement of an incompetent tricuspid valve, which may be delivered by transcatheter placement. It comprises two stents connected by a bridge spanning the right atrium, and two valves anchored by the stents in the superior and inferior vena cavas.
Further, WO 2004/093638 discloses a device and methods for treatment of tricuspid regurgitation, where a first and a second stented valve are implanted at the superior and inferior vena cava. The device is intended to permit blood flow towards the right atrium of a patient and prevent blood flow in the opposite direction.
Nevertheless, the currently available devices and their handling imply complicated deployment methods, making a smooth and fast valve replacement difficult to achieve.